1. Field of the Invention
The present invention falls into the area of the further processing of printed products and relates to a method for optical detection of a position of print shop products according to the preamble of patent claim 1 and to an apparatus for optical detection of a position of print shop products according to the preamble of patent claim 13.
To ensure a desired quality of print shop products during postpress processing, the determination of the orientation and/or the position of printed products is imperative, depending on the case. On account of the often very high processing capacities of currently about 30 000-40 000 copies per hour in high performance systems, non-contacting monitoring system offer advantages, as is known, as compared with mechanical or electromechanical monitoring systems. The prior art discloses a number of optical monitoring systems.
2. Discussion of Related Art
In EP 0685420 B1, for example, it is proposed to subject the part products to optical/electronic monitoring as they are collated, by an image recording device or a reading head registering each part product or a section thereof in synchronism with the delivery cycle. A light emitting means arranged beside the image recording device ensures that the part product or the section thereof is sufficiently lightened. The registered data is processed electronically in an image processing means, by being compared with reference information read in previously or, respectively, a calibration image. If a deliverer or a feed station delivers defective or wrongly oriented part products, then an appropriate control or alarm signal is generated. Since, in the case of this design, it is not possible as a result of the construction to illuminate the part products exactly from the viewing direction of the image recording device in the form of a camera, the illumination is not one hundred percent ideal for the registration by the image recording device.
In DE 10 2007 009 971 A1, a method and an apparatus for recording an image of an edge of a printed sheet are disclosed. An image recording device and/or an illuminating device are guided in parallel and in synchronism with the conveyed sheet. The illuminating device arranged beside the image recording device in this case illuminates a sheet surface in such a way that each sheet edge causes a dark shadowed strip. An image recorded by the image recording device exhibits high contrast between the light sheet and the dark shadow, by using which the sheet edge can be determined by means of electronic image processing.
The known monitoring methods have the disadvantage that the registered images lead to relatively high quantities of data which have to be processed by an image processing unit. Since the apparatus required for this purpose, such as image recording device, image processing unit and data link, has to be correspondingly powerful, it is often costly.